The catalysis of multi-electron redox reactions is a fundamental problem that has been solved in certain biological systems through the agency of multimetallic enzymes (cytochrome c oxidase, laccase, and nitrogenase). The detailed mechanisms by which these metalloenzymes function are still obscure. Our research is directed towards the synthesis of functional biomimetic catalysts for the electrochemical reduction of dioxygen to water (a 4e- process), nitrogen to ammonia (a 6e- process), and the oxidation of hydrogen (a 2e- process). Recently we have developed several functional models for the active site in cytochrome c oxidase. These complexes reduce O2 by 4e- at pH. Our complex that is structurally closest to "the real thing," is the best catalyst. By studying the electrocatalytic reduction of dioxgen in lipid layers under conditions of slow electron delivery, we have shown that Cub and an appended tyrosine (Try-244) is necessary to afford selective 4e reduction of dioxygen at physiological potentials. By using our functional model we are exploring the action of hydrogen sulfide interacting with cytochrome c oxidase. Hydrogen sulfide can produce a state of hibernation in animals, probably by its interaction with cytochrome c oxidase. Understanding this process could lead to drugs that induce hypoxia and may have many medical applications.